A small number of patients with aortocoronary bypass operation were found to develop atherosclerotic lesions in the vein grafts. Risk factors, associated with the development of these lesions, as well as their histologic features will be studied. The socio-economic impact of the aortocoronary bypass operation, as expressed in number of patients retaining or returning to gainful employment will be investigated on the basis of information obtained during the yearly follow-up visits of these patients. And finally, the possible association of blood lipid levels, and other risk factors with the retention or loss of vein graft patency will also be studied. BIBLIOGRAPHIC REFERENCES: Barboriak, J.J., Pintar, K., and Korns, M.E.: Atherosclerosis in aortocoronary vein grafts. Lancet, ii (7881):621-624, Sept. 14, 1974; Rimm, A.A., Barboriak, J.J. and Anderson, A.J.: Risk factors in heart patients with or without demonstrable atherosclerotic heart disease. Fed. Proc., 34:247, 1975. (Abstract).